a) Field of the Invention
This invention relates to pigment compositions, a production process thereof, colorants and colored articles. More specifically, it is an object of the present invention to provide pigment compositions comprising, as a principal component, pronouncedly reddish xcex5-copper phthalocyanine (hereinafter abbreviated as xe2x80x9cthe component Axe2x80x9d or xe2x80x9cthe xcex5-formxe2x80x9d) and suitable for a variety of coloring applications.
b) Description of the Related Art
Among all pigments, copper phthalocyanine pigment is especially stable, is excellent in a variety of fastness, and has many crystal forms. Of these crystal forms, those known to have already found actual industrial use include xcex1-copper phthalocyanine (hereinafter abbreviated as xe2x80x9cthe component A-1xe2x80x9d or xe2x80x9cthe xcex1-formxe2x80x9d), xcex2-copper phthalocyanine (hereinafter abbreviated as xe2x80x9cthe xcex2-formxe2x80x9d), and the xcex5-form. It is a common practice to use the xcex2-form in applications to impart a greenishblue color and the xcex1-form in applications to impart a reddish blue color. The xcex5-form is, however, employed when impartation of a blue color more reddish than that available from the use of the xcex1-form is required.
In a variety of coloring applications, however, there is an outstanding demand to impart a blue color still more reddish than that available from the use of the xcex5-form. Such a pronouncedly reddish color tone cannot be realized with a single copper phthalocyanine pigment. In general, there is hence no choice other than relying upon use of a mixture of copper phthalocyanine and a pigment more reddish than copper phthalocyanine. Mixing of two or more pigments, however, leads to a reduction in tone when they are mixed in the form of powders or colorants and are then used. Therefore, the color tone so obtained is unavoidably accompanied with reductions in saturation and vividness and also with a decrease in transmittance.
With a view to lessening these problems, attempts have been made to mix two or more pigments in the course of conditioning such that the resulting pigment mixture shows a behavior similar to a single pigment. Such attempts include, for example, dry grinding of a phthalocyanine pigment and another pigment into a pigment mixture. Even with the pigment mixture obtained by this method, however, tinting power and vividness are still insufficient.
As a method for lessening the above-described drawbacks of dry grinding and imparting better homogeneity to the resulting mixed pigment, it has also been proposed to produce a pigment mixture by wet grinding. The pigment mixture obtained by this method is excellent in both dispersibility and vividness, but fails to exhibit particularly good properties in heat resistance, solvent resistance, light fastness and weatherability.
Even if the processing of pigments is performed by grinding as described above or by another method, a pigment mixture which can produce the above-described still more reddish blue color cannot be obtained unless the processing forms only the xcex5-crystal form, which shows a blue tone with a reddish-purple tinge, as the crystal form of the processed copper phthalocyanine pigment as a base colorant.
It is also known to form copper a phthalocyanine pigment and another pigment into a pigment composition by dissolving them in sulfuric acid and then causing them to co-precipitate in water. However, the copper phthalocyanine pigment in the pigment composition obtained by this process has all been transformed into the xcex1-form, so that the color tone of the copper phthalocyanine pigment itself as a color base is more greenish than the xcex5-form. This process, therefore, cannot provide a pigment which produces the above-described still more reddish blue color.
An object of the present invention is, therefore, to eliminate the above-described drawbacks of the conventional art and to provide a copper phthalocyanine pigment composition comprising a mixture of the more reddish xcex5-form and another pigment and capable of producing a vivid reddish-blue color.
The present inventors have proceeded with extensive research to achieve the above object. As a result, it has been found that a pigment composition, which comprises the xcex5-form as a principal component and is a more homogeneous mixture, can be obtained by transforming the xcex1-form into the xcex5-form in a pigment mixture of the xcex1-form and another pigment, leading to the completion of the present invention.
The above-described object can be achieved by the present invention to be described hereinafter. Described specifically, the present invention provides a pigment composition comprising a wet-ground pigment mixture of the following components (A) and (B):
(A) xcex5-copper phthalocyanine, and
(B) at least one pigment selected from a group consisting of condensed polycyclic pigments and azo pigments;
wherein a weight ratio of the component (A) to the component (B) is 100:0.1 to 100:50.
A first process according to the present invention for the production of the pigment composition comprises wet-grinding (A-1) xcex1-copper phthalocyanine and the component (B) at a weight ratio of from 100:0.1 to 100:50 in a non-aromatic solvent.
A second process according to the present invention for the production of the pigment composition comprises dry-grinding the components (A-1) and (B) at a weight ratio of from 100:0.1 to 100:50 to obtain a dry-ground pigment mixture; and then wet-grinding the dry-ground pigment mixture in a non-aromatic solvent.
A third process according to the present invention for the production of the pigment composition comprises adding (A-2) copper phthalocyanine of any crystal form and the component (B) at a weight ratio of from 100:0.1 to 100:50 into an at least 60 wt. % aqueous solution of sulfuric acid; pouring the resultant aqueous sulfuric acid solution into water to have the component (A-2) transformed in crystal form into the xcex1-form such that a pigment mixture of the component (A-1) and the component (B) is obtained; and then wet-grinding the thus-obtained pigment mixture of the component (A-2) and the component (B) in a non-aromatic solvent.
In all applications, for example, in coloring plastics, paints, printing inks, textile printing agents, electrophotographic toners, color filters, ink-jet inks, heat transfer inks and the like, the pigment composition according to the present invention is useful as a colorant improved in heat resistance, solvent resistance, light fastness and weatherability while producing a color tone more pronouncedly reddish than conventional copper phthalocyanine pigments without causing reductions in saturation and vividness and a decrease in transmittance.